Ballast water treatment apparatus

ABSTRACT

The present invention provides a ballast water treatment system including a reaction tank in which raw water and ozone are imported and made to react each other for a predetermined period of time to kill microorganisms existing in raw water, an ozone decomposer in which water containing residual ozone discharged from the reaction tank is imported and the residual ozone is decomposed, and a circulation pump installed between the reaction tank and ozone decomposer, forming a circulation system which removes the residual ozone by means of circulating the water containing the residual ozone between the reaction tank and ozone decomposer. 
     Accordingly, this system dispenses with a deaeration tank which would require a wide space for installation, small cost and is able to be applied to existing ships easily.

FIELD OF THE INVENTION

The present invention relates to a ballast water treatment apparatusand, more particularly, relates to a ballast water treatment apparatuswhich can remove ozone remaining in ballast water efficiently at smallcost.

BACKGROUND

Ballast water drained from cargo ships such as container ships containsaquatic organisms and bacteria which inhabit in ports where the ballastwater is drawn and are conveyed to other countries as the ships move.

As seriously considered the above background, a diplomatic conference atthe International Maritime Organization (IMO) adopted the InternationalConvention for the Control and Management of Ships' Ballast Water andSediments to make the obligation of implementing ballast water controlbe applied to ships to be built from 2009 onward.

Consequently, it is required to make it possible to drain such cleanballast water as meets the International Convention for the Control andManagement of Ships' Ballast Water and Sediments.

Accordingly, it is now a matter of great urgency to develop asterilization and/or elimination technology in the ballast water whichcan solve the above problem.

Conventionally, a technology for sterilization by means of injectingozone into ballast water in parallel with injecting steam and furthergenerating micro bubbles of ozone to promote formation of hydoxyradicalsto reduce consumption of ozone has been offered, as seen in UnexaminedPatent Application Publication No. 2004-160437(JP).

SUMMARY

It is inevitable that ozone in the form of fine bubbles remains in theballast water. If this ballast water containing residual ozone is fedinto a ballast tank, it will cause a problem of corroding ballast tanks,transmission pipelines, etc.

It may be considered that corrosion-resistant materials are used forballast tanks, transmission pipelines, etc to solve this problem;however, this measure is expensive and also problematic in that it isnot applicable to existing ships.

When ballast water containing residual ozone is left alone atatmospheric pressure for dozens of minutes, the residual ozone will bedischarged into the air. However, in order to leave the ballast wateralone, it will be necessary to have a tank of large volume whichrequires a wide space to be secured for its installation. It will affectthe construction design of the ship hull to secure a space forinstalling the tank of large volume. In addition, it will be very costlyand, therefore, impractical to install the tank of large volume.

An object of the present invention is to provide a ballast watertreatment system which can remove ozone remaining in ballast waterefficiently at small cost.

Other objects of the present invention will be clarified in thefollowing descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of the present disclosure will be or become apparent toone with skill in the art by reference to the following detaileddescription when considered in connection with the accompanyingexemplary non-limiting embodiments, wherein:

FIG. 1 is a drawing showing the first embodiment of the ballast watertreatment system;

FIG. 2 is a drawing showing the second embodiment of the ballast watertreatment system;

FIG. 3 is a drawing showing the third embodiment of the ballast watertreatment system;

FIG. 4 is a drawing showing the fourth embodiment of the ballast watertreatment system;

FIG. 5 is a drawing explaining the inside of the ballast tank in case areaction tank is a flexible bag; and

FIG. 6 is an explanatory drawing in case a reaction tank is an accordioncylinder.

DETAILED DESCRIPTION

FIG. 1 shows the first embodiment of the ballast water treatment systemrelated to the present invention.

Features 1 are ballast water tanks 1 installed in a ship. Though 8ballast water tanks 1 are installed in this ship, the number of theballast water tanks is not definite. The ballast water to be stored inthe ballast tanks 1 is drawn from a port, etc. by means of driving apump 3 installed on an intake pipe 2. The ballast water is eitherseawater or fresh water.

Feature 4 is an ozonizer. Ozone generated by the ozonizer 4 is mixed inthe ballast water running in the intake pipe 2 by a static mixer (notshown), etc.

Feature 5 is a reaction tank installed outside the ballast tanks 1. Thereaction tank 5 stores the ballast water mixed with ozone for a whileand retains it for a predetermined period of time. The retention time ispreferably 1-15 minutes. This will kill microorganisms and bacteriaexisting in the ballast water by the use of strong oxidizing power ofozone. The reaction tank 5 has an exhaust pipe 7 which has an exhaustvalve 6 that opens when waste ozone inside is discharged outside. Thisexhaust pipe 7 is preferably equipped with an ozone decomposer (notshown) to decompose waste ozone to be discharged.

While a part of the excessive ozone contained in the ballast water isdischarged while the ballast water is retained in the reaction tank 5,other excessive ozone will remain in the ballast water. Therefore, theballast water in the reaction tank 5 after sterilization treatment byozone still includes residual ozone.

The ballast water which has been treated with ozone in the reaction tank5 is transferred from the reaction tank 5 to a circulation pipeline 9 bymeans of driving a transfer pump 8.

The circulation pipeline 9 forms a closed annular waterway whichcirculates the ballast water transferred from the reaction tank 5 bymeans of driving a circulation pump 10 installed on the way outside theballast tanks 1. In this first embodiment the circulation pipeline 9 anda circulation pump 10 constitute a circulating means. Each of theballast tanks 1 is connected to the circulation pipeline 9 with aninflux pipe 12 having a respective on-off valve 11.

The ballast water transferred from the reaction tank 5 into thecirculation pipeline 9 is poured into each of the ballast tanks 1through the influx pipe 12.

The circulation pipeline 9 is provided on the way with an ozonedecomposer 13 filled with a catalyst, etc. to decompose and remove theresidual ozone from the ballast water. Accordingly, the ballast watercirculating through the circulation pipeline 9 can contact the elementsin the ozone decomposer 13.

What should be used as the elements does not matter if they can contactthe ballast water circulating through the circulation pipeline 9 anddecompose and remove ozone remaining in the water. Granular activatedcarbon, zeolite, granite porphyry, etc. may be used, for example.

The ballast water transferred from the reaction tank 5 into thecirculation pipeline 9 by the use of the transfer pump 8 can contact theelements in the ozone decomposer 13 several times if it is circulated inthe circulation pipeline 9 several times by means of driving thecirculation pump 10. The ozone remaining in the ballast water isdecomposed and removed in this process. During this process all theon-off valves 11 are closed, so that the ballast water is not fed intothe ballast tanks 1.

The number and the duration of circulation of the ballast water in thecirculation pipeline 9 are determined according to various conditionssuch as the volume of the ballast water in the circulation pipeline 9,circulation velocity, ozone decomposing capacity of the ozone decomposer13, etc.

More than one ozone decomposer 13 may be installed on the circulationpipeline 9. The ozone decomposers 13 may be installed either in seriesor in parallel.

After the ozone remaining in the ballast water is removed, the on-offvalves are opened one after the other and the ballast water rid of theresidual ozone are poured into the ballast tanks one after the otherthrough the influx pipe 12.

An ozone analyzer 14 is preferably installed in the circulation pipeline9 to determine the density of the ozone remaining in the ballast watercirculating in the circulation pipeline 9. If each of the on-off valves11 is an automatic on-off valve, this ballast water treatment system canoperate automatically from the removal of the ozone remaining in theballast water until the import of the ballast water into each of theballast tanks 1 based on the values measured by the ozone analyzer 14 bycontrolling the on-off valves 11 so as to open one after the other whenthe ozone analyzer 14 sensed that the ozone remaining in the ballastwater has been removed.

The ballast water treatment system of the first embodiment can removethe residual ozone which causes corrosion of the ballast tanks 1 if onlythe ballast water which has been provided with sterilization treatmentby ozone is circulated in the circulation pipeline 9 equipped with theozone decomposer 13. Accordingly, this system dispenses with adeaeration tank which would require a wide space for installation and isable to remove the ozone remaining in the ballast water efficiently atsmall cost.

In addition, since this ballast water treatment system can be made uponly by connecting each of the ballast tanks 1 to the circulationpipeline 9 equipped with the ozone decomposer 13, it can be applied toexisting ballast tanks easily.

FIG. 2 shows the second embodiment of the ballast water treatmentsystem. The numerals identical to those in FIG. 1 represent the samecomponents.

The ballast water which has been provided with sterilization treatmentby ozone in the reaction tank 5 is directly imported by means of drivingthe transfer pump 8 into each of the ballast tanks 1 through the influxpipe 12.

A submerged pump 15 is installed in each of the ballast tanks 1. Thedischarge side of the submerged pump 15 is connected to the ozonedecomposer 17 by the circulation pipeline 16. The submerged pump 15, thecirculation pipeline 16 and the ozone decomposer 17 are immersed in theballast water. In the second embodiment, the submerged pump 15 and thecirculation pump 16 constitute a circulating means.

The ozone decomposer 17 is filled with elements such as a catalyst, etc.to decompose and remove the ozone remaining in the ballast water, as theabovementioned ozone decomposer 13 is. Accordingly, the ballast waterstored in the ballast tanks 1 is sucked into the submerged pump 15 bymeans of driving the submerged pump 15, passes through the circulationpump 16 connected to the discharge side of the submerged pump 15,contacts the catalysts, etc. in the ozone decomposer 17 and then flowsout into the ballast tanks 1 again.

In short, the ballast water is circulated within the ballast tanks 1through the submerged pumps 15 and the circulation pumps 16. The ozoneremaining in the ballast water is decomposed and removed in itscirculation process through contacting the elements such as a catalyst,etc. in the ozone decomposer 17.

Time for circulating the ballast water in the ballast tanks 1 isdetermined according to various conditions including the ballast watervolume, circulation velocity, ozone decomposition ability of the ozonedecomposer 17, etc.

The circulation pipeline 16 and the ozone decomposer 17 may be connectedto the suction side of the submerged pump 15. In addition, more than oneozone decomposer 17 can also be connected to the circulation pipeline 16in series or in parallel.

Each of the ballast tanks 1 is preferably equipped with an ozoneanalyzer (not shown) which measures the density of the ozone remainingin the ballast water to control the driving of the submerged pump 15based on the ozone density values measured by this ozone analyzer.

The ballast water treatment system of this second embodiment can removethe ozone which causes corrosion of the ballast tanks with the ozonedecomposer 17 if only the ballast water which has been provided withsterilization treatment by ozone in the reaction tank 5 is circulatedwithin each of the ballast tanks 1; therefore, this system dispenseswith a deaeration tank which would require a wide space for installationand is able to remove the ozone remaining in the ballast waterefficiently at small cost.

Furthermore, since this ballast water treatment system can be made uponly by installing the submerged pump 15, the circulation pipeline 16and the ozone decomposer 17 in each of the ballast tanks 1, it can beapplied to existing ballast tanks more easily.

The ballast water treatment system of the second embodiment is equippedwith the submerged pump 15, the circulation pipeline 16 and the ozonedecomposer 17 in each of the ballast tanks 1. However, it is enough ifthose components are installed at least in one ballast tank 1 of theballast tanks 1.

FIG. 3 shows the third embodiment of the ballast water treatment system.This ballast water treatment system is equipped with the submerged pump15, the circulation pipeline 16 and the ozone decomposer 17 only in oneballast tank 1A of the ballast tanks 1. The numerals identical to thosein FIGS. 1 and 2 represent the same components.

In this embodiment the ballast water in the reaction tank 5 is importedinto the ballast tank 1A on the left end shown by driving the transferpump 8. The submerged pump 15, the circulation pipeline 16 and the ozonedecomposer 17 are immersed in the ballast water within the ballast tank1A.

The ballast water stored in the ballast tank 1A contacts the elementssuch as a catalyst, etc. loaded in the ozone decomposer 17 in theprocess of its circulation for a predetermined period by means ofdriving the submerged pump 15 and the residual ozone is thus decomposedand removed.

The other ballast tanks 1B and 1C which have not been supplied with theballast water from the reaction tank 5 are supplied one by one with theballast water which have been rid of the residual ozone in the ballasttank 1A through the influx pipe 19 by means of driving the transfer pump18. The emptied ballast tank 1A is supplied again with new ballast waterwhich has been provided with sterilization treatment by ozone from thereaction tank 5 and the residual ozone is decomposed and removed in thesame manner as aforementioned.

The ballast tank 1A is equipped with an ozone analyzer (not shown) tomeasure the residual ozone density in the ballast water within theballast tank 1A. The driving of the pump 18 and the opening and closingof the on-off valves 20 are preferably controlled automatically based onthe ozone density values measured by this ozone analyzer.

The ballast water treatment system of this third embodiment need not beprovided with the submerged pump 15, the circulation pipeline 16 and theozone decomposer 17 in all the ballast tanks; therefore, it can be madeup at smaller cost than the second embodiment.

It will be easily understandable that the submerged pump 15, thecirculation pipeline 16 and the ozone decomposer 17 may be installed inmore than one of the ballast tanks.

In the aforementioned ballast water treatment systems of the first tothe third embodiments the reaction tank 5 is installed outside theballast tanks 1. However, the reaction tank may be installed inside aballast tank 1. Installing the reaction tank inside a ballast tank 1 isfurther advantageous in that the construction design of the ship hull isnot affected.

FIG. 4 shows the fourth embodiment of the ballast water treatmentsystem. In this ballast water treatment system the reaction tank 50 isinstalled inside one ballast tank 1 of the ballast tanks 1. The numeralsidentical to those in FIG. 1 represent the same components.

“Inside one ballast tank 1” as mentioned herein means that the top endof the reaction tank 50 does not protrude over the top end of theballast tank 1. Since the end of the reaction tank 50 does not protrudeover the top end of the ballast tank 1, it is not necessary to move anyexisting structures outside the ballast tank 1 or any structuresadjacent to the ballast tank 1.

This reaction tank 50 also stores ballast water mixed with ozone for awhile and retains it for a predetermined period of time as theaforementioned reaction tank 5 does. This will kill microorganisms andbacteria existing in the ballast water by the use of strong oxidizingpower of ozone.

The reaction tank 50 is provided with an exhaust pipe 52 having anexhaust valve 51. This exhaust pipe 52 protrudes over the ballast tank1. The exhaust pipe 52 is preferably equipped with an ozone decomposer(not shown) filled with elements such as a catalyst, etc. to decomposewaste ozone which is to be discharged.

As ballast water is put in the ballast tank 1, the reaction tank 50 isimmersed in the ballast water and is given buoyancy. Therefore, thereaction tank 50 has little influence on the weight balance of theentire ship, causing few problems to the construction design.

Selection of the materials of the reaction tank 50 may be made inconsideration of corrosion due to seawater.

It is preferable to make the reaction tank 50 shape-changeable becauseit can be installed within the ballast tank 1 without respect to theconstruction and the shape of the ballast tank 1.

The shape-changeable reaction tank 50 is preferably a resin-madeflexible bag or an accordion cylinder.

FIG. 5 shows the inside of the ballast tank 1 in case the reaction tank50 is a flexible bag. The numeral 50 a in the Figure shows the statethat the reaction tank 50 is shrunken in the ballast tank 1 and thenumeral 50 b shows the state that the reaction tank 50 is filled withballast water in the ballast tank 1.

Existing ballast tanks are often equipped with vertical reinforcingbraces inside, which makes it difficult to secure a space for installingthe reaction tank 50. However, the reaction tank 50 in the form of aflexible bag can be easily installed within an existing ballast tankbecause it is shape-changeable.

A flexible bag is preferably made of materials which have strength andcorrosion resistance. For example, a bag formed with a single-layer ormulti-layer synthetic resin sheet or a laminate of synthetic resin andrubber lining can be used.

FIG. 6 shows that the reaction tank 50 is an accordion cylinder. Theaccordion cylinder is in a shrunken state in normal times as shown inFIG. 6(A) and as ballast water is put in, it expands as shown in FIG.6(B).

The height of the reaction tank 50 formed by an accordion cylinder canbe adjusted freely; therefore, it can be installed even if there is anyobstacle above. The accordion cylinder may be laid in the ballast tank1.

It is enough if the reaction tank 50 is installed in any one of theballast tanks 1; however, it may also be installed in each of theballast tanks 1 especially if it has been made shape-changeable. Thereaction tank 50 does not occupy a large space inside each of theballast tanks 1 if it is shrunk after the residual ozone is removed.

The ballast water treatment system of the fourth embodiment does notonly have the effect similar to those of the ballast water treatmentsystems of the first to the third embodiments but also the effect ofdecreasing the influence on the construction design of the ship hull.

This reaction tank 50 may also be installed at least in any one of theballast tanks in the ballast water treatment systems of the embodimentsshown in FIG. 2 and FIG. 3. In this case, the ballast water which hasbeen provided with sterilization treatment by ozone in the reaction tank50 is transferred into the ballast tank equipped with the said reactiontank 50 and into the other ballast tanks by means of a transfer pump.

It may be emphasized that the above-described embodiments, particularlyany “preferred” embodiments, are merely possible examples ofimplementations, merely set forth for a clear understanding of theprinciples of the disclosure. Many variations and modifications may bemade to the above-described embodiments of the disclosure withoutdeparting substantially from the spirit and principles of thedisclosure. All such modifications and variations are intended to beincluded herein within the scope of this disclosure and the presentdisclosure and protected by the following claims.

1. A ballast water treatment system comprising: a reaction tank in whichraw water and ozone are imported and made to react with each other for apredetermined period of time to kill microorganisms existing in the rawwater; an ozone decomposer in which water containing residual ozonedischarged from the reaction tank is imported and the residual ozone isdecomposed; and a circulation pump and circulation piping forming acirculation system which enables the removal of the residual ozone bydelivering the water discharged from the reaction tank containing theresidual ozone to the ozone decomposer.
 2. The ballast water treatmentsystem as set forth in claim 1, wherein the reaction tank is installedoutside ballast tanks.
 3. The ballast water treatment system as setforth in claim 2, wherein the circulation system is installed outsidethe ballast tanks.
 4. The ballast water treatment system as set forth inclaim 2, wherein the circulation system is installed inside the ballasttanks.
 5. The ballast water treatment system as set forth in claim 4,wherein the circulation system is installed in all of the ballast tanks.6. The ballast water treatment system as set forth in claim 4, whereinthe circulation system is installed in one of the ballast tanks.
 7. Theballast water treatment system as set forth in claim 1, wherein thecirculation system is installed outside the ballast tanks, and thereaction tank is installed inside the ballast tanks.
 8. The ballastwater treatment system as set forth in claim 3, wherein inlet pipes areinstalled to connect the circulation system to each of the ballast tanksand an automatic on-off valve is installed on each of the inlet pipes totransfer the treated ballast water rid of the residual ozone to each ofthe ballast tanks one after the other by means of opening and closingthe automatic on-off valves.
 9. The ballast water treatment system asset forth in claim 8, wherein a density sensing means is installed inthe circulation system to measure ozone density values in the treatedballast water rid of the residual ozone, based on which the opening andclosing of the automatic on-off valves is controlled.
 10. The ballastwater treatment system as set forth in claim 1, wherein the retentiontime of the ballast water in the reaction tank is within the range of1-15 minutes.
 11. The ballast water treatment system as set forth inclaim 1, wherein the reaction tank is a flexible bag or an accordioncylinder.